Tesla already has the Model S, and it plans to deliver its Model X SUV next fall. When the company was coming up with a name for its third-generation car, an all-electric sedan with a price tag of about $35,000, it settled on the name Model E–that was, until it bowed out out of its trademark application for the name. But why the letter “e”? Because CEO Elon Musk has a childish sense of humor.

“A friend asked me at a party, ‘What are you going to call the third-generation car?’ Well, we got the S and the X–we might as well make it an E. It kind of stuck,” he said. For fun, Musk said the company had also contemplated trademarking the Model Y name. “Things are pretty dry in the trademark world. Nobody picked up on that.”

However, plans to spell out “sex” with Tesla’s lineup were scrapped when Ford, which also applied to trademark the Model E name, rang up the electric car company. Musk said Ford threatened litigation (it’s unclear if he was joking), but the official stance is that the two companies settled things amicably. (Ford has attempted to trademark the Model E name multiple times, dating as far back as 2000.)